Add is_required column to pp_shop_products_custom_fields table

This commit introduces a new column `is_required` to the `pp_shop_products_custom_fields` table. The column is of type TINYINT, cannot be null, and has a default value of 1. This change is intended to enhance the product custom fields by allowing the specification of whether a field is mandatory.

templates/shop-product/_partial/product-custom-fields.php

@@ -1,10 +1,10 @@
 <? if ( is_array( $this -> custom_fields ) ): foreach ( $this -> custom_fields as $custom_field ):?>
   <div class="custom-field">
     <div class="_name">
-      <?= $custom_field['name'];?>:
+      <?= $custom_field['name'];?><? if ( !empty( $custom_field['is_required'] ) ): ?>*<? endif; ?>:
     </div>
     <div class="_input">
-      <input type="text" class="form-control" name="custom_field[<?= $custom_field['id_additional_field'];?>]" field_name="<?= $custom_field['name'];?>" value="">
+      <input type="text" class="form-control" name="custom_field[<?= $custom_field['id_additional_field'];?>]" field_name="<?= $custom_field['name'];?>" value="" <? if ( !empty( $custom_field['is_required'] ) ): ?>required<? endif; ?>>
     </div>
   </div>
 <? endforeach; endif;?>

templates/shop-product/product.php

@@ -526,7 +526,7 @@
       }
 
       // dodatkowe pola muszą być uzupełnione
-      $( '.custom-field input' ).each( function( index, element )
+      $( '.custom-field input[required]' ).each( function( index, element )
       {
         if ( $.trim( $( element ).val() ) == '' )
         {